Liquid fuel composition



Patented Mar. 28, 1944 Lr'omnFUEr. COMPOSITION Walter A. Schulze andJoseph Preston Lyon, Jr.,

Bartlesvllle, kla., a'ssignors to Phillips Petroleum Company, acorporation of Delaware No Drawing. Application April 4, 1940. SerialNo. 327,912

Claims.

This invention relates to a liquid 'hydrocarbon motor fuel composition,and to the method of preparing said composition. Mpre specifically, thisinvention relates to the preparation of special hydrocarbon motor fuelscontaining tetraethyl lead in stable solution therein.

There are certain types of motor fuels such as high-octane aviationgasolines which are manufactured and blended accordingito specificationsso strict that the selectiongof suitable components for blending islimited to synthetic or naturally occurring substantially purehydrocarbons. Such blends must have high octane rating, because thetetraethyl lead content is limited, and accordingly, the hydrocarbonconstituents of the blend must have an excellent response to addition ofantidetonant. Further, the olefinic or other unsaturated hydrocarboncontent of the fuels must be almost nil, of the order of less than oneper cent in order that the fuels be substantially free of gum and ofsusceptibility to gum formation. Also the absence of olefinichydrocarbons is desirable because olefins contribute to excessive enginecylinder temperatures during combustion and are not very responsive tolead-alkyl antidetonant compounds.

Such fuels are satisfactorily blended only from natural or synthetic,high-octane aliphatic or cyclic paraflin hydrocarbons although certaincarefully selected aromatic compounds such as toluene may be used insome instances. The resuiting blends of practically pure saturatedhydrocarbons are substantially non-gum-forming and have an adequateresponse to the lead-alkyl antidetonant. From the standpoint of storagestability, the outstanding possibility of deterioration of such a fuelin storage is the loss of octane number caused by loss of antidetonantcompound by precipitation from the fuel, and such deterioration is thesubject of this invention.

It is an object of this invention to stabilize aviation gasolines whichdo not contain substantial amounts of highly unsaturated, gum-forminghydrocarbons such as olefins and diolefins and the like, and whichcontain an antidetonant.

Another object of this invention is to provide a stable solution-oftetraethyl lead in special motor fuels, composed of substantiallynon-gumforming saturated hydrocarbons with olefinic content of less thanone per cent, which have a tendency to deposit the antidetonant asinsoluble residues.

A further object of this invention is to we vent the separation orprecipitation of leadalkyl antidetonant compounds trom substantiallynon-gum-forming hydrocarbon motor fuels which have a measurable tendencyto precipitate said antidetonant compounds and thereby lose theantidetonant effect.

Other objects and advantages will become apparent from the followingdisclosure and discussion.

In the manufacture of very high octane motor fuels, such as to 100octane number aviation gasolines, because of the limitation ontetraethyl lead addition the procedure usually includes the manufactureof synthetic isoparaflins. For example, such manufacture may include thepolymerization of isobutylene to form isooctenes, followed byhydrogenation of the polymers to form isooctanes, with less than one percent residual unsaturation.

These synthetic hydrocarbon fuels havingan octane number of to may thenbe blended with suitable saturated hydrocarbon stocks to meet thespecifications governing volatility and vapor pressure. To such a blendis then added a quantity of an antidetonatlng agent such as tetraethyllead calculated to result in an octane number within the desired range.

The gasoline stocks which are suitable for use in such blends arecarefully selected and are usually limited to saturated hydrocarbonliquids such as light straight-run naphthas which may containcyclo-paraffins and suitable fractions of natural gasolines which arepredominantly aliphatic in nature, although certain non-gumformingaromatic hydrocarbons such as toluene may be used, providing such usedoes not infringe any specifications for the fuel. The selection of suchstocks, mainly pure hydrocarbons, with only negligible amounts ofunsaturates and other impurities, is necessary because the finishedblends must meet very stringent specifications regarding acid heattests, gum content and gum formation in storage.

The purity and inherent stability of fuels prepared by theabove-outlined procedure, or the various possible modifications, is wellillustrated by the following abstract of U. S. Army Specifications No.2-92-A. The fuel must yield less than 6 milligrams of residue per 100cubic centimeters, after evaporation of a portion of a 200 cubiccentimeter sample which has been heated at 210 F. in contact with 35square inches of steel surface for 5 hours under 100 pounds per squareinch oxygen pressure/i A fuel passing such a test must certainly bejudged substantially gum-free and non-gum-forming.

We have found that such fuels in spite of inch oxygen pressure purity,selected composition and inherent stability often exhibit a seriousdegradation; that ing agent such as tetraethyl lead often show atendency to suffer the precipitation of insoluble residues from thetetraethyl lead under certain storage or test conditions such as theexposure to heat, oxygen and steel. same fuels, before'the addition ofsuch an antidetonating agent, substantially lack the tendency to formgums, and do not contain appreciable quantities of olefins or dioleflnsor the like which ordinarily cause, or contribute to the formation ofgum.

* We have now discovered that the precipitation of lead compounds fromliquid fuels of the type described which have a tendency to cause "or toallow said precipitation may be prevented by the addition to the leadedfuel of small amounts. of an efllcient anti-oxidant, or gum-inhibitor,such as are available in commercial form to the in- On the other hand,the v is, the finished fuels containing an antidetonatdustry and such ashave been used heretofore only in fuels containing gum-forminghydrocarbons.

The function of the inhibitor is, in the light of-the foregoing'description, not to prevent gum formation, since thehydrocarbon liquidsof our composition are substantially non-gumforming. In some manner,which is-not precisely known to us, these added compounds are ableeither to maintain in their original form the solvents for theantidetonant or to stabilize directly the antidetonant compound andprevent its deterioration or chemical change.

The amount of inhibitor or anti-oxidant which we find effective in ourcomposition is extremely small, being of the order of about 1 to 4 ormore pounds of inhibitor per 1000 barrels of gasoline or in other termsbetween about 0.0001 and 0.002 per cent by weight of the fuel. Thesequantities are based on the'use-of anti-oxidants approximatel'y aseffective as monobenzyl-para-aminophenol, a widely used gum inhibitor.With less eillcient anti-oxidants larger quantities may be required. Theaddition of the preferred quantity of anti-oxidant produces nodeleterious effect on the fuel since other qualities are unimpaired.

Since it is common commercial practice to pur chase and use saidinhibitors as solutions of varying concentrations in suitable solvents,it should be stated for the purpose of clarity that these preferredquantities are exclusive of the weight of such solvents or othermaterial of like nature.

The means of adding the anti-oxidant to the liquid fuel may be anyconventional method known to the industry, is generally just before orjust of the tetraethyl lead composition, as may be convenient ordesirable. After the fuel is thus blended, it .is found that theconditions which would formerly cause precipitation of lead compounds inthe uninhibited fuel no longer do so. Thus, exposure to the conditionsof the previously mentioned gum test (U. S. A'rmy No. 2--92'-A) nolonger causes any precipitation of insoluble lead compounds from thegasoline.

The following examples of the eillcacy of our composition are includedhere, not [as limiting our invention, but to illustrate some of thepossible benefits. Many other analogous modifications and uses of ourprocess will b obvious tothose skilled in this art.

Components and finished blends, of aviation gasoline were prepared andheated to 210 F. in a glass-lined bomb under .100 pounds per square incontact with steel surface and the time of addition after the additionfor 5 hours. The following observations were made:

3 cc. TEL/gallon.) l4 anti-oxidant(isobutylp amino phenol.

None Lead precipitate (dc- Isooctane base+20% creased oct. N0.)

pentane-free natural gasoline-Hi cc.. TEL/gallon.

Isooctane based-20% 0.00l5% Dupont No. No precipitate.

pentanc-iree nat- /9 anti xidant (nural gasoline+3 cc. butyl-p-aminophe-TEL/gallon. 1101). 100 octane fuel (with 0.0004% Dupont No. Do.

3 cc. TEL/gallon). l4 anti-oxidant (iso bult)yl-p-aminophcno In order tomeasure any corresponding efiect on lead content occurring with ordinarymotor fuels containing cracked gasolines which range from 10 to per centor more in unsaturation, induction period tests were made on severaltypical fuels. These tests included placing the sample of gasoline in aglass-lined bomb under 100 pounds per square inch oxygen pressure andheating the bomb at 210 F. until there was a rapid absorption of oxygenby the sample. After the test, the gasoline samples were examined, andwhile there was in some cases a resinous organic deposit, there was noevidence of substantial precipitation of lead residues. The results ofthese testsindicat that in ordinary cracked gasoline there is onlynegligible tendency to precipitate the antidetonant compound, whereas,in the case of pre dominantly saturated and substantially non-gumformingaviation gasolines, thelead-precipitating tendency is greatly magnified.

The inhibitors which we find mosteffective in our composition aremonobenzyl-para-aminophenol and homologous substituted aminophenols suchas are commerciailyavailable to the industry.

Further, we disclaim all benefits and previously disclosed effects ofthe use of said gum inhibitors for the prevention or reduction of gumformation in motor fuels containing larg amounts of cleflnic, dioleflnicand other unsaturated gumfcrming hydrocarbons and gum-formingimpurities. We emphasize the fact that the fuels to which we add saidinhibitors are of such character'as to of our. special fuel compositionare sufficient to distinguish over ordinary gum-forming fuels containinggum inhibitors.

What we claimis: p

1. An improved aviation gasoline having an octane number above- 80,comprising essentially a non-gum-forming hydrocarbon fuelcontainin lessthan one perv cent by volume of oleflnic or diolefinic hydrocarbons,tetraethyl lead and an aminophenol of the group consisting of mono:benzyl-para-aminophenol, isobutyl-para-aminophenol, and normallmtyl-para-aminophenol in 'an' amount equal to between about weight percent of'the fuel asessentially the sole added material tending toinhibit decomposition and precipitation of said tetraethyl lead.

2. The method of preventing the precipitation be classified assubstantially non-gum-forming, and that the qualities and uses a ofinsoluble lead compounds which tend to precipitate from a blend oftetraethyl lead antidetonant in essentially non-gum-forming aviationgasolines containing less than one per cent by volume of oleflnic orother unsaturated hydrocarbons, which comprises adding to such agasoline a small amount of an aminophenol of the group consisting 'ofmono-benzyl-para-aminophenol, isobutyl-para-aminophenol, and normalbutylpara-aminophenol as essentially the sol added material tending toprevent the precipitation of the antidetonant compound.

3. The method of stabilizing aviation gasolines having an octane numberabove 80 and composed of essentially non-gum-forming hydrocarbons, withan olefinic or other unsaturated hydrocarbon content of less than oneper cent, and tetraethyl lead which comprises adding to such a gasolinebetween 0.0008 and 0.002 weight per cent of monobenzyl-para-amino-phenolas essentially the sole added material tending to inhibit decompositionand precipitation of said tetraethyl lead, whereby the precipitation ofoil-insoluble lead compounds is inhibited.

4. A motor fuel composition, comprising essentially hydrocarbons in theboiling range of motor fuel and of such a character as to be classifiedas substantially non-gum-forming, an antidetonant compound which tendsto decompose and b precipitated when in admixture with such hydrocarbonsunder normal conditions of storage and handling of aviation motor fuel,and a small amount of an aminophenol of the group consisting ofmonobenzyl-para-aminophenol, isobutyl-para-aminophenol, and normalbutyl-paraaminophenol as essentially the sole material tending toinhibit said decomposition and precipitation of said antidetonant.

5. A motor fuel composition, comprising essentially hydrocarbons in theboiling range of motor fuel and of such a character as to be classifiedas substantially non-gum-forming, an antidetonant compound which tendsto decompose and be precipitated when in admixture with suchhydrocarbons under normal conditions of storage and handling of aviationmotor fuel, and a small amount of monobenzyl-para-animophenol asessentially the sole material tending to inhibit; said decomposition andprecipitation of said antidetonant.

6. A motor fuel composition, comprising essentially hydrocarbons in theboiling range of motor fuel and of such a character as to be classifiedas substantially non-gum-forming, tetraethyl lead which tends todecompose and be precipitated when in admixture with such hydrocarbonsunder normal conditions of storage and handling of aviation motor fuel,and a small amount of an aminophenol of the group consisting ofmonobenzylpara-aminophenol, isobutyl-para-aminophenol,

and normal butyl-para aminophenol as essentially the sole materialtending to inhibit said decomposition and precipitation of saidtetraethyl lead.

7. A motor fuel composition, comprising essentially hydrocarbons in theboiling range of motor fuel and of such a character as to be classifiedas substantially non-gum-forming, alead-alkyl antidetonant compoundwhich tends to decompose and be precipitated when in admixture with suchhydrocarbons under normal conditions of storage and handling of aviationmotor fuel, and a small amount of an aminophenol of the group consistingof monobenzyl-para-aminophenol, isobutylpara-aminophenol, and normalbutyl-paraamino phenol as essentially the sole material tending toinhibit said decomposition and precipitation of said antidetonant.

8. A motor fuel composition, consisting essentially of paraflinhydrocarbons in the boiling range of motor fuel and containing less thanone per cent by volume of unsaturated hydrocarbons, a lead-alkylantidetonant compound which tends to decompose and form precipitate whenin ad mixture with such hydrocarbons under normal conditions of storageand handling of aviation motor fuel, and a small amount of anaminophenol of the group consisting of monobenzylpara-aminophenol,isobutyl-para-aminophenol, and normal butyl-para-aminophenol asessentially the sole material present tending to inhibit saiddecomposition and precipitation of said antidetonant.

9. A motor fuel composition, comprising essentially hydrocarbons in theboiling range of motor fuel and of such a character as to be classifiedas substantially non-gum-forming, a lead-alkyl antidetonant compoundwhich tends to decompose and be precipitated when in admixture with suchhydrocarbons under normal conditions of storage and handling of aviationmotor fuel, and a small amount of isobutyl-para-aminopheno1 asessentially the sole material tending to inhibit said decomposition andprecipitation of said antidetophenol as essentially the sole materialtending to inhibit said decomposition and precipitation of saidantidetonant.

WALTER A. SCHULZE. JOSEPH PRESTON LYON, JR.

